Two years ago, the Associated Press won the Pulitzer Prize for investigative reporting for its article on the deaths of South Korean refugees at a bridge near the town of No Gun Ri during the early weeks of the Korean War.

The story described events that took place nearly half a century earlier, painting a brutal picture of retreating American GIs ordered by their commanders to kill Korean civilians.

Korean citizens, who later filed claims against the governments of the United States and South Korea, said as many as 400 were killed, 300 under a bridge at No Gun Ri and 100 more in a strafing run by U.S. Air Force planes. The AP reporters said the American soldiers they interviewed said as many as 200 were killed.

The story appeared on Sept. 29, 1999, caused a big fuss and was featured prominently in newspapers all over the United States, including on Page 1 of the New York Times.

Now, one of the three AP writers, Charles Hanley, is apparently trying to suppress publication of a new book -- "No Gun Ri: A Military History of the Korean War Incident" -- that takes another view of what happened at No Gun Ri. The book, written by U.S. Army Maj. Robert Bateman, is highly critical of the AP story, calling into question the reporters' sources and research. But Bateman's book isn't the first time the AP story has been criticized.

By May 2000, barely a month after the three AP writers were awarded their Pulitzer, journalism's highest award, challenges to the AP investigation had begun to appear, most notably in U.S. News & World Report and on the now- defunct Web site stripes.com. It was the start of a skirmish between the AP and critics of the No Gun Ri story that's still going on.

The Pulitzer Prize, like many high-profile contests, is not immune to squabbles. This year, Laura Landro of the Wall Street Journal has challenged a Seattle Times series on the Fred Hutchinson Cancer Research Center in Seattle, where she was treated in 1992 for cancer. Times officials, who submitted the series for a Pulitzer, immediately said Landro had a conflict of interest because of her relationship with the center.

The No Gun Ri dispute between Bateman and Hanley is equally contentious.

Late last year, Hanley wrote a nine-page letter to Stackpole Books, the Pennsylvania publisher bringing out Bateman's book this month, saying it would be a "grave mistake" to publish Bateman's "diatribes and defamations." A copy of the letter, filled with personal attacks against the author, was made available to The Chronicle.

The letter is the kind of dark threat that gives free speech experts the chills -- "an effort at prior restraint," said Bill Kovach, chairman of the Committee of Concerned Journalists -- not to mention the fact that in this case, there is a certain reversal of roles.

"It's ironic for a journalist, someone whose livelihood is protected by the First Amendment, to be seemingly threatening to curtail the speech of a military person," said James Naughton, president of the Poynter Institute, a journalism school in St. Petersburg, Fla. "The way matters like this tend to get resolved over time is for people to be able to make their own judgments about which version of events holds up on examination. More access to publishable versions, rather than less, seems to be desirable."

At Harvard, Bob Giles, curator of the Nieman Foundation for Journalism, said that books about events that happened 50 years ago draw "on the memories of many people who may or may not have been participants. So it's a subject of continued historical and scholarly investigation. Think of all the versions we have of events leading up to Pearl Harbor."

"It seems to me to be out of bounds for one author to try to short-circuit the publication of another author's book," said Chris Finan, president of the American Booksellers Foundation for Free Expression. "It's extraordinary and alarming."

For his part, Hanley said in an e-mail message to The Chronicle, "It is more than appropriate for me to defend my professional reputation and the reputations of my colleagues against a man who . . . has attacked our integrity based on nothing more than his own wild imaginings and ignorance."

Hanley learned of Bateman's work on No Gun Ri after Bateman circulated early drafts of his material to historians, journalists and veterans of the 7th Cavalry. Hanley says the veterans "called my attention to" Bateman's book.

Hanley says Bateman's version of what happened at No Gun Ri is "simply a vicious attack on us (the AP writers) personally, with fantasies about our psyches and motivations, about our mysterious evil journalistic methodologies, and about the dark secrets he imagines we're keeping.

"It belongs on the science fiction shelf," Hanley wrote in the e-mail.

He said Bateman's publisher is "free to publish whatever it wants." But he decided to write the publisher anyway because "obviously, if you care about your own good reputation and the truth, you would lay out the facts so that anyone considering perpetuating this stuff would know he's handling material rife with falsehoods."

Publishers say pre-emptive strikes against forthcoming controversial books happen more often than one might think. "It is not unusual when somebody discovers they're the subject of a book, and they don't like it, to attempt to influence what will be published," said Peter Osnos, a longtime reporter for the Washington Post who now runs PublicAffairs, a New York publishing house.

"To intervene and try to assert (your point of view) is an acceptable if not necessarily attractive part of the process," Osnos added. "I don't think what Hanley did is an outrage. It clearly reflects his genuine anguish over the subject."

Kovach, a former Nieman curator, said, "I don't see anything wrong with engaging with the author of another book, pointing out errors," adding that he was "a little concerned" over a journalist trying to "balk publication."

"It's crossing a magic line," Kovach said. "I just think any effort at prior restraint is anathema to the whole concept of free flow of information."

The dispute between Bateman (who is now at the Center for Strategic and International Studies in Washington on a year-long fellowship) and Hanley started in the fall of 1999 as a civil discussion by phone and e-mail, not long after the AP story appeared. Bateman, at the time an Army captain teaching history at West Point, was already familiar with the 7th Cavalry Regiment, a legendary Army unit involved in everything from Custer's last stand to Korea to the intense battle in Vietnam's Ia Drang Valley, now the subject of the Mel Gibson movie, "We Were Soldiers." (As a sidelight showing the inevitable six degrees of separation, one of Hanley's harshest critics is Joseph L. Galloway, co-author of the best-selling book from which the movie was made, and also author of the U.S. News & World Report piece that took Hanley and his AP cohorts to task in May 2000. And the introduction to Bateman's new book was written by retired Army Lt. Gen. Harold Moore, Galloway's co-author and the battalion commander played by Gibson in the movie. )

When Bateman was a company commander in the 7th Cavalry between 1994 and 1996, he became good friends with Edward Daily, well known in the military establishment as the author of two books on the 7th Cavalry and as a past president of 7th Cavalry veterans' associations. To the young captain, Daily was a shining example of what the Army wants its people to be, a man to be looked up to, maybe even a hero. When Daily visited Fort Hood, Texas, where the 7th Cavalry was stationed, Bateman escorted him around the post.

After the AP's No Gun Ri story was published, Bateman was surprised to find that Daily had been interviewed by the AP and that he had told the news agency about the killings, said he was there, saw it all, heard the cries of dying babies. Daily became one of the chief public faces of the story -- NBC News took him to South Korea with anchorman Tom Brokaw to do a "Dateline" show on No Gun Ri and the Washington Post profiled him.

But some of the particulars about Daily just didn't seem to ring true to Bateman -- details about how officers give orders, how the military chain of command works and Daily's own military career.

Bateman turned to B.G. Burkett, a Texas stockbroker and Vietnam veteran who has become nationally known for exposing phony veterans. Burkett is co-author of "Stolen Valor," a book about how he outed hundreds of braggarts who lied about their military careers.

With Burkett's help, Bateman began searching through government and other records and interviewing Korean War veterans. The more he looked, the more he became convinced that there was something wrong with the AP's story. The AP, for its part, has vigilantly defended its reporters' work. And Pulitzer Prize administrators said they saw no reason to ask the AP to return its coveted prize.

Nonetheless, with Burkett, Bateman discovered that Daily, the 7th Cavalry veteran, had not been what he claimed -- he had not been an officer, he had not been captured by the enemy, he had not received the nation's second- highest decoration for valor and, most importantly, he had not been at No Gun Ri July 26-29, 1950, the time frame of the incident.

After the critics weighed in on the AP story, the news agency played down Daily's importance. But before this and other discrepancies surfaced in the spring of 2000, Hanley told Bateman, in one of their e-mail exchanges in March 2000, back when they were friends, that it would be a "superhuman hoax" for Daily to have concocted his military history.

Turns out that Daily was quite capable of concocting that hoax and persuading the Veterans Administration to pay him benefits and give him free medical care from 1986 until the end of 2001. A month ago, Daily pleaded guilty in federal court in Nashville, Tenn., to defrauding the government of $412,839 in veteran's benefits and medical care.

And he admitted to federal agents that "he had not participated in the alleged massacre at No Gun Ri," according to James Vines, the U.S. attorney in Nashville.

In January 2001, the Army completed its investigation of No Gun Ri and said that although it could not "determine what happened near No Gun Ri with certainty, it is clear, based upon all available evidence, that an unknown number of Korean civilians were killed or injured . . ." Bateman puts the number at "between eight and 35."

The Army also found that despite "some conflicting statements and misunderstandings," investigators concluded that U.S. officers never issued "oral or written orders to shoot and kill Korean civilians" at or near No Gun Ri.

These days, the main battle of No Gun Ri is about Bateman's book. Edward Skender, the editor of Stackpole Books, declined to talk about the feud or Hanley's letter.

But in a letter he sent Hanley in December 2001, Skender wrote that "there are now at least four versions of the events at No Gun Ri -- the Koreans', yours, the (U.S. Army's) and now Robert Bateman's.

"Historians, journalists and veterans are likely to argue over this incident for years to come, and there will undoubtedly be more books and articles written about it."

And Finan, the booksellers' free-speech expert, said, "You have to let the books speak for themselves. That's what the First Amendment is all about. It's the public that makes the final decision of truth."